Blotting paper as a disposable tool for sampling chemical residues from skin surface

摘要

Collection of sufficient amounts of chemical residues andmetabolites from skin in a non-invasive manner is challenging[1]. The available sampling methods are based on theuse of various sampling techniques [2]: macroduct, solventextraction, tape stripping, oil/membrane approach, implementingabsorbing materials such as semipermeable skinpatch, alcohol swab, cotton pad, textile, nitrocellulose membrane,or imprinting materials such as silica plate, polydimethylosiloxanefilm and derivatized silicon. In certaincases, specimen collection is invasive while some materialscause inconvenience due to the time-consuming samplingstep. In the past few years, our laboratory developed hydrogelmicropatch sampling method, which was successfully combinedwith mass spectrometry (MS) allowing for detection ofskin metabolites [3], disease biomarkers [4], and topical drugs[5]. The previous method took advantage of an atmosphericpressure sample introduction to MS without pre-separation.In fact, such hassle-free interfaces are popular in the MSrelatedresearch work [6,7]. However, eliminating the chromatographicseparation step complicates quantitative analysisof complex samples by increasing the risk of isobaricinterferences. Another drawback of our previous method wasfast drying of the hydrogel (agarose), what put an additionalburden on the analyst (preparation of the probes a few hoursbefore sampling skin). In an attempt to address these issues,we have been searching for a better sampling material, and weintended to use it in combination with a hyphenated analyticaltechnique. In principle, one could consider hundreds ofsynthetic materials (e.g. polymers) as potential sorbents forskin sampling. While a major limitation of implementing newsynthetic materials in clinical applications is theirbiocompatibility [8], various commercially available skin-careproducts can potentially be used to collect molecules presenton the surface of skin for chemical analysis. In this study, weshow that oil-control blotting paper can lift chemical speciesoriginating from a topical agent from skin in the quantitiessufficient for subsequent analysis by gas chromatography (GC)coupled with MS (Fig. 1A). Due to the great popularity of plantbasedinsect repellents [9], we exemplify the use of the proposedprotocol by investigating retention of such a repellenton the surface of skin. The knowledge of the retention kineticsof the related topical agents on the skin can be useful for thedevelopment of more effective formulations with long retentiontimes, anddin consequencedfor more efficient protectionagainst infectious diseases spread by insect vectors.